PROJECT SUMMARY/ABSTRACT Rates of opioid overdose (OD) deaths have risen drastically in the US over the last decade; Massachusetts (MA) is one of the hardest hit states, ranking 7th in age-adjusted OD death rate. Clinical care innovations have led to effective interventions; unfortunately, these innovations have not become standard in many MA communities. Using the Communities That Care (CTC) model, MassHEAL experts and community stakeholders will utilize a data-driven approach to identify and narrow service gaps to tailor and implement a suite of programs to reduce OD deaths in MA by 40% in 3 years. Key components will include identifying people with opioid use disorder (OUD); providing OD risk reduction; and accelerating access to low-threshold initiation of medications for OUD (MOUD) for high-risk individuals during hospitalization, incarceration, and opioid detoxification. Sixteen highly impacted communities have been identified across MA. MassHEAL will use a cluster-randomized parallel group design with communities randomized 1:1 to the intervention arm (office-based addiction treatment [OBAT] PLUS external facilitation for communities to select from a menu of programs and strategies, n=8) vs. a control arm (OBAT only, n=8). The MA Public Health Data (PHD) Warehouse, which links individual-level data from more than a dozen state agencies, is a unique resource available only in MA permitting pragmatic assessment of community- and individual-level outcomes. The MassHEAL team exemplifies the multi-disciplinary expertise and collaborative experience necessary to execute this study successfully. It includes clinicians who specialize in safer opioid prescribing and treatment of OUD and have developed many of the programs proposed. This clinical team is complemented with health services researchers, public health professionals, biostatisticians, community engagement specialists, implementation scientists, and health economists in order to evaluate the intervention comprehensively. Using principles of community-based participatory research (CBPR), MassHEAL has established a Community Advisory Board that will support effective community?academic partnerships. The Specific Aims are: 1) employ community engagement principles to develop and implement tailored clinical, prevention, and communication strategies in MassHEAL intervention communities; 2) determine the impact of the MassHEAL intervention on opioid OD deaths and other outcomes; 3) measure the impact of external facilitation on communities' success implementing an OUD prevention and treatment intervention; and 4) estimate the value of the MassHEAL community intervention relative to standard of care. MassHEAL will implement and assess a menu of evidence-based programs to reduce opioid OD deaths in highly impacted communities across MA. Results of this study will inform the broad dissemination and implementation of innovative medical and public health strategies to achieve the aims of the HEALing Communities initiative across the US.